How great would it be to be a fly on the wall as some of the biggest companies are developed? Or to hear about the challenges entrepreneurs have faced on the road to their first million? Last week at the third annual Chicago Ideas Week, a group of successful entrepreneurs opened up about how they created their companies, shared the successes and struggles faced along the way, and the lessons learned from the experience. Here are their pearls of wisdom:

1. Accept failure as part of the journey."The great ones treat failure as a necessary part of their journey. It's not win or lose. It's always win or learn," says Eric Lefkofsky, CEO of Groupon. Lefkofsky shared several anecdotes of past ventures that failed, including Brandon Apparel Group and Starbelly, which he says led him to the brink of bankruptcy in 2001. That year, he started InnerWorkings, a print procurement company that was a success. Lefkofsky insists there was no magic to what worked and what didn't. He kept working and trying new things until eventually he developed InnerWorkings and things clicked.

2. Keep your eyes open for opportunities.For the founder of Honest Tea, inspiration came at the grocery store. Dr. Barry Nalebuff, a professor at Yale School of Management, was just looking for a good glass of tea. While there were dozens of beverage options already in the marketplace, Nalebuff found water was boring, soda to be liquid candy, and diet drinks dangerous.

He applied economic theory to the beverage market, and found that the best product should be less sweet: Less calories for the customer, less cost for the manufacturer. Nalebuff knew tea was the world's cheapest luxury good, and teamed up with a former student, Seth Goldman, to create Honest Tea in 26 days back in 1998 (they sold Honest Tea to Coca-Cola in 2011). Nalebuff calls it the "Princess and the Pea" theory, after the children's tale: "If something out there's annoying you, that's an opportunity," Nalebuff says.

3. When opportunity knocks, be ready for it.After Honest Tea launched, Nalebuff was at a yoga retreat and noticed Oprah Winfrey on a nearby mat. Because he always carried samples with him everywhere he went, Nalebuff offered Winfrey a drink, and Honest Tea was subsequently featured in her magazine. "When opportunity strikes, you have to be prepared for it," Nalebuff says.

4. There's no set path to success."There's no set path to success, there are many ways to get there." says Dan Gilbert, founder of Quicken Loans and a principal of Detroit Venture Partners, an organization that funds start-ups and is leading revitalization efforts in Detroit. Gilbert says he's most proud of creating an environment that lets his employees sell and listen to customers. Both he and Quicken Loans' CEO answer complaint calls. When asked what drives him, Gilbert says, "I like to build. Most entrepreneurs at their core like to build."